Generally, a social networking service (SNS) is a service for linking users based on existing relations between friends or relatives. In a SNS, a user tends to communicate with another user dependent on existing relations (see, for example, JP2008-140246A).
However, communication based on existing relations has some disadvantages. For example, past actions in a SNS such as making a comment or posting information (especially, information a user may not wish others to become aware of) may be accessible to another user with whom the user has existing relations. Relations between users tend to continue until one of the users ends the relations.
In addition, some users may wish to have an opportunity to meet people with whom they are not acquainted. However, if people who are not acquainted with each other have little in common it may be difficult for such people to communicate effectively.